Atmospheric pathways for pollutant emission and deposition are under intensive study both in the U.S. and abroad. U.S. Government involvement was established by the Acid Precipitation Act of 1980 and resulted in the establishment of the U.S. Interagency Task Force on Acid Precipitation. The private sector is represented by the Electric Power Research Institute (EPRI). The issues involved are complex, with economic, social and political implications that transcend geopolitical and regional boundaries. In North America, airborne pollution originating from coal-fired electric power plants in the Midwestern U.S. is thought by many to be responsible for damage to the environment and to architectural structures in the Northeastern U.S. and Southeastern Canada. Similar issues have been raised in Western Europe. Regulatory agencies require detailed and accurate information on this phenomenon in order to establish effective guidelines for controlling the problem. The electric power industry needs similar information in order to make sound decisions regarding the economic and engineering aspects of pollution abatement technologies.
Acid rain, as it is called, is primarily an atmospheric phenomenon which implies large-scale and complex behavior. Thus far, the most ambitious attempts to characterize the transport and deposition of these pollutants have used tracer gases released into exhaust plumes, downwind (ground based) detector arrays, and airborne detectors. These studies have produced useful information, but it is known that as much as half of the total sulfate deposited is in the solid state in the form of sub-micron particulates. Gaseous tracers are not well suited for modeling the transport and deposition of solid state pollutants. Particulate tracers, such as oil fog, smoke and die particles, have been used in tracer experiments, but all have drawbacks.